The present invention relates to a characteristic amount sensor, and more particularly to a piezoresistance type pressure sensor or the like used for process control and an acceleration sensor or the like used for automobiles, etc.
It is known that a zero point of a sensor output shows hysteresis, when gauge resistors provided on a semiconductor substrate are wired such that, for example, an aluminum wiring provided on a pressure sensor presents a yield phenomenon by a temperature cycle. A conventional solution is to provide a high concentration impurity diffused layer p.sup.+ having the same conductivity as a p-type gauge resistance to extended to a pad portion replacing aluminum wiring. Such a solution is described in JP-B-3-6674.
The conventional technique described above has a large effect of reducing temperature hysteresis since there is no aluminum wiring. On the other hand, however, a normal value of the sheet resistance of the high concentration impurity diffused layer (the p.sup.+ layer) is approximately several ten .OMEGA./SQ, which is several hundred times as large as that of aluminum. Thus, when the high concentration impurity diffused layer is extended so as to connect between gauge resistances or between bonding pads, there has been such a problem that the effective sensitivity of the gauge resistance is lowered because the connecting portion is a stress insensitive portion.
Further, a means for widening the p.sup.+ layer is conceivable in order to lower the resistance value of the connecting portion, but there has been such a problem in this method that a leakage current between the substrate and the high concentration impurity diffused layer is increased.